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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Johan Hovold <johan@kernel.org>
Subject: [PATCH 4.17 26/67] USB: serial: keyspan_pda: fix modem-status error handling
Date:   Mon, 16 Jul 2018 09:34:55 +0200
Message-Id: <20180716073447.271347846@linuxfoundation.org>
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4.17-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Johan Hovold <johan@kernel.org>

commit 01b3cdfca263a17554f7b249d20a247b2a751521 upstream.

Fix broken modem-status error handling which could lead to bits of slab
data leaking to user space.

Fixes: 3b36a8fd6777 ("usb: fix uninitialized variable warning in keyspan_pda")
Cc: stable <stable@vger.kernel.org>     # 2.6.27
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/usb/serial/keyspan_pda.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/usb/serial/keyspan_pda.c
+++ b/drivers/usb/serial/keyspan_pda.c
@@ -369,8 +369,10 @@ static int keyspan_pda_get_modem_info(st
 			     3, /* get pins */
 			     USB_TYPE_VENDOR|USB_RECIP_INTERFACE|USB_DIR_IN,
 			     0, 0, data, 1, 2000);
-	if (rc >= 0)
+	if (rc == 1)
 		*value = *data;
+	else if (rc >= 0)
+		rc = -EIO;
 
 	kfree(data);
 	return rc;